Not related to TK or Miles&Smiles but Pegasus Airlines's sale for this year would be 50% off on international routes ( ex-AYT direct and TRNC routes excluded ) for travel between 12 April 2020 and 30 June 2020.

I have checked some routes and when clicking on the 50% discount, the base fare never decreases 50% but significantly less. I haven't tried doing dummy bookings on expensive days.